Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 04/10/85

Final Date: 07/22/87

Deleted Date:

The Naval Air Station (NAS) Moffett Field site is located 35 miles south of San Francisco and approximately 1 mile south of San Francisco Bay in Santa Clara County, California. The former Navy installation consists of approximately 1500 acres and is bounded by former evaporation salt ponds to the north, Stevens Creek to the west, U.S. Highway 101 (Bayshore Freeway) to the south, and the Lockheed Martin Aerospace facility to the east. NAS Moffett Field was commissioned in 1933 to support the "lighter than air" (LTA) program. Two years later the LTA program ended, but to support World War II, the LTA program was reactivated and a "heavier than air" program began to support fighter planes. The station became the largest naval air transport base on the west coast.

The Navy participated in the Installation Restoration Program, a specially funded program established by the Department of Defense (DOD) to identify, investigate, and control the migration of hazardous contamination at military and other DOD facilities. To date, 30 hazardous waste sites have been identified at the NAS Moffett Field site.

Ongoing work is being conducted at eight of these sites. The eight sites are:

Site 1 - Runway Landfill (part of Operable Unit 1)

Site 22 - Golf Course Landfill

SIte 25 - Eastern Diked Marsh and Stormwater Retention Basin

Site 26 - East-side Aquifer Treatment System Area (also referred to as the EATS Area)

Site 27 - Northern Channel

Site 28 - West-Side Aquifers Treatment System Area (also referred to as the WATS area)

Site 29 - Hangar 1

Orion Park Area (Currently owned by the U.S. Army)

Groundwater in the underlying aquifers beneath the site is not used for drinking water or other potable uses. Groundwater in the area is, however, a potential future source of drinking water and therefore groundwater cleanup standards have been established.

Contaminants and Risks

Contaminated Media

Groundwater

Surface Water

Air

Soil and Sludges

Environmentally Sensitive Area

Impacts at the NAS Moffett Field site consist of soil and groundwater contamination from both petroleum products and volatile organic compounds (VOCs) such as trichloroethene (TCE) and tetrachloroethene or perchloroethene (PCE). There are also two landfills and one former landfill at the site. Sediments are contaminated in wetland areas of the base, primarily in outfall areas. The prime contaminants in the sediments are polychlorinated biphenyls (PCBs) and pesticides. The site is adjacent to other Superfund sites in the Middlefield-Ellis-Whisman (MEW) study area and Moffett Field's underlying groundwater is contaminated by activities from both operations.

Who is Involved

This site is being addressed through federal actions. EPA is the lead regulatory agency overseeing the Navy's environmental investigation and cleanup work at NAS Moffett Field Superfund Site. The Regional Water Quality Control Board (Water Board) is the state support agency.

Investigation and Cleanup Activities

Initial Actions

Initial Actions: Abandoned wells that may be potential conduits for subsurface cross-contamination have been evaluated and properly closed. Initial source control measures were implemented at Sites 12 and 14 include bioremediation of contaminated soil and treatment of groundwater through carbon absorption. These interim activities were completed in 1996. A groundwater extraction and treatment system was implemented at Site 9 (west side aquifers) and closed in mid-1997 to allow operation of a long-term groundwater extraction and treatment system that operates in conjunction with the MEW Regional Groundwater Remediation Program.

Site Studies

Base-Wide: In 1989, the Navy began a thorough investigation to determine the type and extent of contamination base-wide. The areas investigated included: east and west side contaminated soils, the westside aquifers, the eastside aquifer, three landfills and the wetlands area.

Site Studies

In 1984, the Navy began environmental restoration at NAS Moffett Field. The initial study included a review of available records on the handling of chemicals, interviews with site personnel, and a visual survey of activities conducted at the site. Other investigations have been conducted to assess potential source areas of contamination and the type and extent of contamination.

NAS Moffett Field was designated a closing base under the Base Realignment and Closure Act (BRAC II). Please see the Navy's Moffett Field web site for additional detailed information about environmental cleanup at the site.

Cleanup Results to Date

An overview of each active site at NAS Moffett Field is provided below. These overviews include information about the investigation and cleanup activities that are planned or underway.

Site 1 - Runway Landfill (part of Operable Unit 1)

Site 22 - Golf Course Landfill

SIte 25 - Eastern Diked Marsh and Stormwater Retention Basin

Site 26 - East-side Aquifer Treatment System (also referred to as EATS)

Site 27 - Northern Channel

Site 28 - West-Side Aquifers Treatment System (also referred to as the WATS area)

Site 29 - Hangar 1

No Further Action Sites

Petroleum Sites

Operable Unit 1 – Landfill Sites 1 and 2
Site 1 is a 12-acre landfill that was used for the disposal of refuse and scrap equipment. It operated from the mid-1960s to the late 1970s. Site 2 was a 1-acre landfill used between the 1940s and 1952. The combined sites are known as Operable Unit 1 (OU1). Potential contaminants at Site 1 include volatile organic compounds (VOCs) (thinners, solvents, lacquer), petroleum products (oil, fuel filters), pesticides, sawdust contaminated with transformer oils (possibly containing PCBs) and paints. Site 2 reportedly received the same types of waste as Site 1.

The Final Record of Decision (ROD) for OU1 was signed in 1997 and required consolidation of refuse from Site 2 with that at Site 1, as well as a multilayer cap to contain the wastes. Refuse from Site 2 was removed, the wastes were placed in the Site 1 landfill and the landfill was “capped.” Soil samples collected from the Site 2 excavation verified that all wastes had been removed. The Site 2 area was backfilled with clean material, and a fence was installed around the site to restrict access. Groundwater at Site 2 was tested quarterly through 2002. Test results consistently showed no contamination.

EPA and the Water Board approved closure of Site 2 in early 2003. Because contaminants were removed, Site 2 was “clean closed” and is available for unrestricted use.

At Site 1, the multilayer landfill cap was completed in November 1998. Long-term maintenance of the cap and monitoring of landfill gas and groundwater at Site 1 began in 1999, to make sure the landfill was not emitting unacceptable levels of gas and that contaminants were not getting into the groundwater or San Francisco Bay. Raptor perches were installed to naturally control burrowing animals, such as rodents and ground squirrels, that could damage the landfill cap. Several types of hawks and a golden eagle have been seen using the perches. These perches, in combination with other measures, have been successful in controlling ground squirrels. The California Integrated Waste Management Board inspected the cap and, in March 2000, approved the site’s closure.

Two Five-Year Reviews for OU1 were completed in 2002 and 2007. The remedy continues to be protective of human health and the environment. The Navy continues to maintain the Site 1 landfill cap and monitor landfill gas and groundwater. In 2004, the monitoring changed from quarterly to semiannually based on 5 years of sampling data confirming that contaminants were not being released to the environment. The Santa Clara County Department of Environmental Health inspects Site 1 quarterly and periodically conducts landfill gas monitoring. All landfill gas monitoring results showed only very low emissions, well within safe limits.

Site 22 – Golf Course Landfill
The Site 22 landfill covers 11 acres. The Navy operated the landfill from about 1950 to 1967, mainly for domestic waste disposal. The waste is buried at least 3 feet below the ground surface. By 1973, the Site 22 landfill had been converted into holes 3, 6 and 7 of the Moffett Field Golf Course. Between 1994 and 1999, the Navy conducted soil and groundwater studies, called a remedial investigation, and identified the type and extent of contaminants throughout the site. Soil and groundwater at Site 22 contain VOCs, semivolatile organic compounds and pesticides. Shallow groundwater beneath the landfill is not used for drinking water. Groundwater monitoring is being conducted to make sure contaminants are not migrating from the site.

The studies also evaluated the potential for landfill gas to build up and migrate from the site. It was found that landfill gases are not escaping into the air or moving underground beyond the site. The studies concluded that as long as the landfill waste remains buried, there is no risk to human health or the environment. However, burrowing animals such as ground squirrels, were bringing refuse to the surface, which created a potential risk to human health at the golf course. This was the primary concern for the site and the focus of the cleanup action.

The selected cleanup remedy, a biotic barrier made of gravel and cobblestone was documented in a ROD, which was signed in June 2002 by the Navy, EPA and Water Board. “Biotic” refers to the fact the barrier will keep out animals. Construction of the biotic barrier was completed in August 2003 and is described in the Navy's April 2004 Remedial Action Report. The biotic barrier covers the refuse while allowing the landfill to be used as part of a golf course.

Regular maintenance and long-term monitoring of groundwater and landfill gas is ongoing at Site 22, as required under the September 2003 Post-Construction Operations, Maintenance, and Monitoring Plan. A Five-Year Review for the Site 22 Landfill was completed in 2008. The remedy continues to be protective of human health and the environment.

Site 25 – Eastern Diked Marsh and Stormwater Retention Pond

Site 25, located in the northwestern portion of Moffett Field, includes NASA's 175-acre Stormwater Retention Pond and the Eastern Diked Marsh, as well as approximately 52 acres belonging to the Midpeninsula Regional Open Space District (MROSD). Site 25 has been used for the past 50 years by the Navy and NASA to manage stormwater at Moffett Field. Levees border the north and east sides of the Stormwater Retention Pond and the west side of the MROSD parcel. These levees provide flood protection for Moffett Field and adjacent properties. Historical photographs reveal that levees, blocking the area from tidal flow, were built before Moffett Field was developed.

The environment at Site 25 is commonly called a “seasonal wetland” (the area is wet for most of the year due to rainfall but dries out for a certain amount of time each summer or fall). As a result, Site 25 had been evaluated for a cleanup remedy that would make the site safe for the existing seasonal wetland ecosystem. NASA intends to change the site use to a “managed pond.” This area will serve as the stormwater retention pond during the winter and be kept wet during dry months via a connection to San Francisco Bay. The other property owner, MROSD, plans to convert its property to a “tidal marsh” by connecting it to San Francisco Bay.

The Navy evaluated cleanup scenarios that would allow a managed pond, tidal marsh, and seasonal wetland. The evaluation included learning what plants and animals live in managed ponds and tidal marshes as compared to seasonal wetlands. It also involved figuring out the chemical levels that are safe for these plants and animals. Due to changes in projected future ecological use at the site, the Feasibility Study (FS) was amended with an FS addendum in 2007. Based on the FS addendum findings, the Navy issued a Proposed Plan in January 2009. The Proposed Plan recommended restoring Site 25 to a tidal marsh by excavating contaminated sediments, treating certain areas with lead and zinc contamination, and disposing of the sediments off-site. Following a public comment period on the Proposed Plan, the Navy, with EPA concurrence and State consultation, selected this final cleanup approach in a Record of Decision (ROD) for Site 25 in 2009. Site 25 cleanup was completed in 2013.

Site 26 -East-Side Aquifer Treatment System (EATS) Area
The EATS area is located on the east side of Moffett Field, northeast of Hangar 3. Chlorinated solvents (TCE and PCE) were used at Hangars 2 and 3 and contaminated the groundwater underneath the site. TCE and PCE, as well as their breakdown products (cis-1,2-dichloroethene, 1,1-dichloroethene and vinyl chloride), were identified in groundwater. The groundwater in the area is not used for drinking water, and no buildings are located over the EATS site. An ecological risk assessment showed that plants and animals are not at risk from contaminants in groundwater.

The cleanup remedy for the EATS area began operating in January 1999. The remedy includes a groundwater extraction and treatment system consisting of five extraction wells and an air stripper with carbon treatment. Groundwater is constantly pumped from each extraction well and is treated to remove the contaminants. The treated water is discharged to the Moffett Field storm drain system. In 2003, EPA and the Water Board approved the EATS Evaluation Work Plan for collecting data to evaluate the effectiveness of EATS. The data would also be used to evaluate other possible methods to clean up the groundwater. In July 2003, EATS was temporarily turned off to evaluate conditions when no groundwater extraction was occurring.

The first Five-Year Review Report for the EATS area, a major milestone document, was approved by EPA in September 2005. The report recommends completing the work outlined in the EATS Evaluation Work Plan, which would include nutrient enhancement to speed up contaminant breakdown by naturally occurring microorganisms. In February and March 2005, nutrients, consisting of a product made from corn and corn-based oil, were injected into two "hot spot" areas of groundwater. The nutrients slowly release lactic acid, which is “eaten” by microorganisms in the groundwater. The microorganisms ultimately break down the solvents in the groundwater, cleaning it up.

Groundwater has been monitored for the last several years after the nutrient injection to make sure that it is working. In 2008, the Navy finalized an evaluation report for the EATS area and proposed conducting a treatability test of an in-situ alternative technology in a "hot spot" area of the groundwater contamination plume. EPA approved the workplan and sampling plan and the Navy started the test in 2009. Results are back and the Navy is in the process of amending the ROD to select the final remedial approach.

Site 27 - Northern Channel
Site 27 consists of the Northern Channel and the associated ditches: Marriage Road Ditch, Patrol Road Ditch and the North Patrol Road Ditch, all of which drain into the Northern Channel. The Northern Channel is located at the northeastern end of Moffett Field, bordered on the north by ponds managed by the U.S. Fish and Wildlife Service (formerly Cargill Salt evaporation ponds), to the south by Moffett Field and, as the channel extends east, Lockheed Martin property. The property owners of the Northern Channel have included Cargill Salt, Lockheed Martin, NASA and the City of Sunnyvale. In addition to the surface water collected by these ditches, the Northern Channel receives stormwater through a system of surface channels and french drains (under the runway); this stormwater is pumped into the channel by the Building 191 lift station. This system is designed to control flooding on the east side of Moffett Field.

The 2005 ROD for Site 27 documents the cleanup remedy, which includes the removal of contaminated sediment in the channel and ditches to protect the site’s ecosystem. Active excavation of contaminated sediment and soils was completed in January 2007. The Navy completed site restoration activities at Site 27 and finalized its Remedial Action Completion report inApril 2012.

Site 28 - West-Side Aquifers Treatment System (WATS) Area
The WATS area is located on the west side of the runways, near Hangar 1. Potential sources of groundwater contamination in the WATS area include a former dry cleaning facility (chlorinated solvents), former fuel storage and wash rack facilities (petroleum hydrocarbons) and former manufacturing facilities south of Moffett Field (chlorinated solvents). In 1994, the Navy removed contaminants in the soil under Building 88; the process included the demolition of Building 88 and removal of an associated tank and sumps. The Navy began groundwater extraction and treatment in the Building 88 area the same year.

Contamination from dry cleaning activities at Building 88 and fuel operations has mixed with a VOC plume originating from the MEW Superfund Study Area located just south of Moffett Field. The MEW Study Area is named by the streets that generally bounds the area - Middlefield Road, Ellis Street, and Whisman Road . The companies responsible for investigating and cleaning up the MEW Site are collectively called the MEW companies. The contamination plume co-mingled with Navy and MEW contamination is referred to as the “regional groundwater VOC plume” or regional plume. See the Middlefield-Ellis-Whisman (MEW) Study Area for more information.

The Navy’s groundwater extraction and treatment system is an integral component of the regional groundwater remediation program. WATS began operating in November 1998. WATS consists of nine extraction wells and a groundwater treatment system located west of Hangar 1. The extraction wells constantly pump approximately 70 gallons of contaminated groundwater per minute. This water is treated to remove the contaminants and then discharged to the Moffett Field storm drain system. The groundwater treatment system includes an advanced oxidation process and granular activated carbon (GAC) vessels. The GAC vessels were added in July 2001 to “polish” the treated water. The majority of the VOCs are chemically changed into carbon dioxide and water, and any remaining contaminants are removed in the GAC vessels. The Navy modified the treatment system in May 2003 to eliminate VOC air emissions by removing the system’s “air stripper.”

The Navy began optimization efforts later in 2003 to accelerate cleanup of the site. This work included adding the ninth extraction well and collecting data for further evaluation of the former dry cleaning facility, Building 88. Results of work completed in December 2004 indicated that more fieldwork was needed to evaluate potential sources apparently originating from the Building 88 area. The Navy completed an additional investigation of the former Building 88 area in 2005 and EPA is working closely with the Navy on implementing a pilot test to reduce mass and cleanup the groundwater faster in this area.

Site 29 - Hangar 1
Hangar 1 was constructed in 1932 to house the giant airship U.S.S. Macon. Its floor space covers 8 acres (or the equivalent of 10 football fields) and it stands 200 feet high. Over the years, the hangar provided space for maintenance of aircraft, training facilities and offices for both the Army and Navy. Hangar 1 is part of the property transferred to NASA Ames Research Center in 1994. It formerly housed the Moffett Field Historical Society Museum and was used as a display space for air shows, open houses and various commercial and public functions.

The building materials and paint used to construct Hangar 1 contain PCBs, asbestos, lead and zinc. The hangar is aging and its paint and building materials are deteriorating. As a result, the contaminants in these materials moved into the environment around the hangar and, ultimately, reached Site 25 through the Moffett Field storm drain system. To ensure the protection of human health and the environment, in 2003 the Navy completed an interim control measure called a time-critical removal action. This included applying a specialized coating to the exterior surface of Hangar 1 to seal the materials on the building surface.

In 2007, the Navy issued a draft revised Engineering Evaluation/ Cost Analysis (EE/CA) recommending removal of the Hangar 1 siding and coating the structural steel frame. The previous EE/CA (2006) had recommended complete demolition of the Hangar. The Revised EE/CA was finalized in July 2008. In January 2009, the Navy signed an Action Memorandum (AM), which declared that the Navy will proceed with the proposed EE/CA alternative, removing the siding and coating the frame. The Navy has completed the action and the structure is now awaiting a reuse plan by NASA, which will hopefully include re-skinning of the Hangar.

No Further Action Sites
Extensive study and evaluation of six sites showed that they could be recommended for “No Action.” According to federal law, No Action is appropriate for sites that do not present a potential threat to human health or the environment. The No Action sites at NAS Moffett Field are:

The east-side soils required no action (1994 OU2-East Record of Decision)

In 2001, EPA and the Water Board agreed with the Navy and the sites were recommended for no further action in the Revised Final Station-wide Feasibility Study Report and its final addendum. The Navy issued a Proposed Plan for public review to provide information about the sites and the proposed decision, held a comment period and a public meeting, and issued a Responsiveness Summary responding to all comments received. On August 22, 2002, a ROD was signed documenting the No Action decision. These sites are now closed.

Petroleum Sites
The petroleum sites at NAS Moffett Field are being addressed under the California Leaking Underground Storage Tank Program, which is specific to petroleum-contaminated sites. Numerous underground storage tank/above ground storage tank cleanup activities are occurring, but have been removed from CERCLA through the Petroleum Exclusion. The State of California has lead oversight authority for petroleum product remediation. While these regulations are fully protective of human health and the environment, they do not fall under CERCLA.

Documents and Reports

Community Involvement

Public Meetings: EPA has awarded a Technical Assistance Grant (TAG) to the Pacific Studies Center. The TAG provides money for activities that help the community participate in decision making at the Moffett Field site. Please contact Lenny Siegel at 650-961-8928 or LSiegel@cpeo.org for more information.

A community advisory group, the MEW Community Advisory Board, meets to learn about and discuss MEW Superfund Study Area cleanup issues.